Figure F13. Close-up photographs of intervals (A) 172-1064A-1H-6, 92-102 cm, and (B) 172-1064A-1H-4, 119-129 cm, containing sharp contacts (indicated by arrows) associated with color changes. (A) shows a sharp contact (arrow) overlain by visible silt laminae, each about 1 mm thick. (B) shows a sharp contact (at 125 cm) that is not associated with any visible structure.